Doors without prominently painted outline can be seen here:

Rear door without prominent outline.

Front door without prominent outline.

Emergency exits without prominent outlines over the wing.
Cabin doors / emergency exits with prominent outlines visible from distance help rescuers in locating them for entering the aircraft in emergency situations especially in dark / poor light.
For example, here's photo of PIA Airbus A310-308 (AP-BDZ) with prominently outlined cabin doors and emergency exit over the wing.
Click here to see large photo.
Abbas

